I run my humidity anywhere from 45% to 60%. It is usually around 100% humidity here in the summer but I keep my 'bators in the middle of the house and they do fine. My friend brought me her still air LG 'bator because she could never get any hatches from it. I have been putting her eggs in it for a few months and get at least a 50% hatch rate for her, more often 65%. I do not care for the still air. In my big sportsman I get closer to a 98% hatch rate, depending on the eggs being set like shipped or my own.
I have opened my big Sportsman many a time and see the gauge saying 25% humidity. Whoopsie! I add water and it goes on just fine.
I have heard that you need to spray duck eggs for added moisture but I never have and get a 98% hatch rate with those, too, in my Sportsman. I can see how you should since I notice my Muscovy girls taking a bath and then while wet going back to sit on their eggs.